Ground-mobile vehicles, such as lawn maintenance equipment like lawn mowers of the commerical nature having a number of mowers, that is, gang mowers, commonly employ hydraulic apparatus for controlling and powering the mowers. In that type of equipment, there is a potential to have hydraulic fluid leaking from the hydraulic apparatus, and of course the hydraulic fluid will leak onto the turf and will be destructive. Commercial lawn mowers are relying more and more on hydraulics, but one problem with the hydraulics, particularly when mowing well-maintained and excellent turf, is that if there is hydraulic leakage, damage is done to the turf because of hot hydraulic fluid dropping onto the fine turf.
The prior art has systems installed on the equipment for the purpose of detecting hydraulic fluid leakage, and these systems operate so that they signal leakage only when it exists at a specific amount.
In contrast to the prior art, which is seen as one example in U S. Pat. No. 4,591,837, the present invention provides a hydraulic system leak detector wherein the detector does not rely on liquid volume changes created by thermal expansion or contraction nor on the liquid volume changes created by hydraulic cylinder actuation.
In approaching the solution to the problem of leakage, questions arose such as what quantity of leakage was sufficiently significant to detect and over what period of time did that leakage occur. Accordingly, leakage can be quantified in terms of hydraulic volume per unit of time. In this analysis, it was determined that monitoring flow rates of the liquid exchanged between two hydraulic tanks provided a system which could be employed to satisfy the detection requirements mentioned above.
Accordingly, the present invention provides for a hydraulic leak detector, particularly one that can be used for golf course greens and the like where the mowers are hydraulically controlled and hydraulically powered and where a leakage of hot hydraulic fluid can damage the turf. The detector of this invention is arranged with two liquid tanks and with passageways and controls therebetween to maintain pressure equilibrium betweem the two tanks. Specifically, this is achieved through detecting a flow-rate from a secondary tank into the main tank when the pressure equilibrium of the two tanks is upset, and the flow-rate detector energizes a switch which can signal the flow-rate and thus detect the leakage.
The present invention further distinguishes over the prior art in that the present invention does not utilize a liquid float member for detecting the level of the hydraulic fluid in a tank. One explanation of this improvement is that a float can become unreliable, or even stuck, when the mobile vehicle on which the tank is mounted is on a hillside or other non-level support. In contrast, the present invention utilizes a flow switch which is not affected by the mobile unit and its tank being off a level orientation.
Additionally, the present invention provides a leak detector wherein the detection is above a pre-selected flow rate datum and at which a flow switch will actuate an electric signal, such as a lamp, and, if the flow persists for a pre-selected time, then, a second signal, such as an audible alarm, will be energized, all to give the operator two different warning signals with regard to the flow rate of the hydraulic fluid between the two tanks. Subsequently, the flow switch will automatically reset itself and the lamp will be de-energized when the flow rate subsides below the datum.